As soon as you enter the route, May/Brendan will talk with you. She/He will heal up your Pokemon and give you HM04 Strength. Follow the main path and you'll find other trainers along the way.
Camper Larry (Reward: p288)
Picnicker Carol (Reward: p304)
After climbing up the hill, you'll find two more hikers that you can battle. You can't access the cable cars at the moment since they're being blocked by Team Aqua members. Enter the fiery cave for now.
Hiker Trent (Reward: p544)
Hiker Brice (Reward: p576)
Even if you have Strength, you won't be able to use it until you get a new badge so ignore the large boulder for now. The path is short and straightforward and you'll reach the other side of Route 112 in a few seconds. As soon as you emerge from the Fiery Path, another trainer will challenge you to battle. North of the thug are three berry trees. Collect Razz Berry x4, and Persim Berry x3. Continue east until you reach the northern part of Route 111.
Street Thug Jaylin (Reward: p672)
Sorry, I went the other way and a different city